The subject invention is directed toward the art of ink jet printers and, more particularly, to an improved ink jet cartridge for a print head of an ink jet printer.
Ink cartridges for ink jet printers generally include a housing containing a bag filled with ink. One such cartridge is shown in EP-A-519457 in which the edge of an aperture of the ink filled bag is imperviously sealed with a protrusion on the bottom of the housing. On the protrusion there is mounted a vacuum valve in the form of a slotted bubble. The valve is arranged between the interior of the bag and a small chamber, which is closed off in the bottom of the housing by means of a sealing plug. During installation of the cartridge in a print head, the plug is pierced by a hollow needle. The print head is then supplied with ink from the bag via the valve and the chamber. The slotted bubble ensures a certain underpressure in the chamber so that the ink does not run out of the print head. With growing underpressure, the slotted bubble becomes deformed so that the slot opens and additional ink flows into the chamber and thus to the print head. However, the underpressure in the chamber generated within the slotted bubble is not accurately adjustable because it depends upon many factors, such as material, shape, wall thickness of the bubble, positioning of the slot, etc.
Another ink jet print head ink cartridge including a bag which holds ink and a vacuum valve between the interior of the bag and a smaller chamber communicating with the orifice plate is shown in EP-A-238829. In this case, the vacuum valve consists of a mushroom-shaped, elastomer body whose central region or stem is fastened to a bottom surface of a valve seat. The periphery of the plate-shaped portion of the elastomer body abuts, under pre-stress, the underside of the valve seat. The valve seat has penetration openings about its periphery through which the ink passes from the interior of the bag to the smaller chamber. With this ink cartridge, the adjustment of the desired underpressure in the smaller chamber below the vacuum valve is relatively imprecise, inasmuch as the ink flows through the weakest point along the relatively long periphery of the plate-shaped elastomer body.